In U.S. patent application Ser. No. 07/079,610 filed on July 30, 1987 entitled "Stone Destroying Catheter", assigned to the same assignee as this invention, and whose disclosure is incorporated by reference herein, there is disclosed and claimed a catheter and method of use for effecting the destruction of a stone or other hard body, e.g., a body containing calcium, located within a living being.
The apparatus comprises a small diameter instrument, e.g., a catheter, having an elongated portion including a longitudinal axis and having a working head located at the distal end thereof. The elongated portion is capable of being located at a position within the body so that the working head is adjacent the stone. The working head comprises a pair of blade-like impacting members. Each blade-like member has an elongate impacting surface. The blades are arranged to move from a retracted position, wherein the impacting surface of each is located adjacent the periphery of the elongated portion of the apparatus, to an extended position, wherein the impacting surface extends substantially beyond the periphery of the elongated portion of the apparatus. The working head is arranged to be rotated at a high speed about the axis. When the working head is rotated the blades are in the extended position. Each impacting surface is arranged when rotated about the axis in the extended position to impact the stone to disintegrate or otherwise destroy the stone. The blades are oriented in a screw pitch so that when the working head is rotated they produce a powerful vortex flow in the fluid surrounding the stones which serves to draw the stones into the blades. In order to guide the stones toward (into) the rotating blades, while also protecting the surrounding body tissue from being damaged by the rotating blades, the catheter also includes shroud/guide means located adjacent the working head.
The shroud/guide means is expandable from a compact state to an expanded state. When in the compact state the shroud/guide is of an outside diameter no greater than that of the catheter to facilitate the placement of the catheter at the situs of the stone to be destroyed.
The catheter is particularly suited for destroying gallstones within the gall bladder with minimum invasion of the patient's body. As is known, gallstone are loose hard bodies located within the gall bladder, an extremely fragile, hollow structure. The catheter is arranged to be introduced while in its compact, blade-retracted state percutaneously and threaded through the patient's liver and through a small opening or puncture in the gall bladder so that the working head extends into the liquid therein. The shroud/guide means is arranged to be moved to the extended state once the working head of the catheter is in position within the liquid in the interior of the gall bladder. The catheter is then operated, that is the motor started, so that the working head commences rotation at a high rate of speed, e.g., from 5,000 to 100,000 rpm. This action causes the blades to move to the extended position.
When the shroud/guide means is in the expanded position it serves to protect the fragile wall of the gall bladder from the rotating blades. In addition, the shape of the shroud/guide means serves to direct the stones toward the rotating blades in cooperation with the vortex produced by the rotation of the blades in the liquid. Large stones which cannot fit fully into the interior of the shroud/guide means are nevertheless held within its open mouth so that the portion of the stone extending therein can be impacted by the rotating blades. This action reduces the size of the large stone, so that it can pass through the mouth fully into the blades, whereupon it is ultimately disintegrated or destroyed.
The vortex created within liquid in the gall bladder recirculates that liquid and the stones into the rotating blades so that their impacting surfaces can repeatedly impact the stones to progressively reduce the size of the stones by pulverization or fragmentation.
In order to expedite the destruction of the stones, the catheter can be utilized in conjunction with a suitable stone dissolving solvent. Such a technique may effect a more rapid disintegration of the stones as a result of the violent agitation and impaction caused by the blades, than could be otherwise achieved by the introduction of a solvent alone. Thus, a central passageway is provided down the catheter to be used to carry any suitable solvent for aiding in the destruction of the stone into the gall bladder.
After running the catheter for a predetermined period of time, e.g., ten minutes, the fluid and pulverized material produced during the stone disintegration process can be extracted or sucked out of the bladder through the catheter and fresh solvent thereafter introduced therethrough. This procedure is then repeated until all of the stones are disintegrated or destroyed.
The use of the shroud/guide means by protecting the delicate wall of the gall bladder enables the catheter to be left operating in place for a sufficiently long period of time, e.g., one hour or more, to ensure that all of the stones are destroyed or reduced to an acceptable size.
While the invention of the aforementioned patent application is suitable for its intended purposes it nevertheless leaves something to be desired from the standpoint of speed or efficiency of operation. In particular, it has been found that in gall stone lithotrite (destruction) applications, if the flow rate of the liquid in the gall bladder is increased (such as could occur by increasing the rotational speed of the working head and/or increasing the rate of flow of liquid introduced and withdrawn from the gall bladder) the faster moving liquid may carry the particles created by the stone destruction process into contact with tissue of the bladder with sufficient momentum to damage that tissue. Moreover, increasing the rate of rotation of the working head and/or the rate of flow of liquid past it results in the formation of a boundary layer of liquid flow contiguous with the blades. That boundary layer may cause the stone particles to slip by the blades and thus not be engaged by their impacting surfaces. Obviously, such action is counter productive to efficient stone destruction.